Part 1: Just started — no badges

Just started — no badges opens 10 areas. There are 45 trainers standing in them. The fights at this checkpoint are Rival Brendan (Mudkip), Rival Brendan (Torchic), Rival Brendan (Treecko), and 3 more.

Where to go

Petalburg City
Wild: Corphish 100% · Lv 20-45, Marill 100% · Lv 5-35, Magikarp 70% · Lv 5-10, Goldeen 30% · Lv 5-10
Pick up: TM42 Facade, HM03 Surf
Rusturf Tunnel
Wild: Whismur 100% · Lv 5-8
Trainers: Hiker Mike Lv 16, Team Aqua Grunt Lv 11, Team Magma Grunt Lv 11
Pick up: HM04 Strength
Petalburg Woods
Wild: Zigzagoon 30% · Lv 5-6, Wurmple 25% · Lv 5-6, Shroomish 15% · Lv 5-6, Cascoon 10% · Lv 5 +3 more
Trainers: Bug Catcher James Lv 8, Bug Catcher Lyle Lv 3, Team Aqua Grunt Lv 9, Team Magma Grunt Lv 9
Route 101
Wild: Wurmple 45% · Lv 2-3, Zigzagoon 45% · Lv 2-3, Poochyena 10% · Lv 2-3, Mudkip Lv 5 +2 more
Route 102
Wild: Corphish 100% · Lv 20-45, Marill 99% · Lv 5-35, Magikarp 70% · Lv 5-10, Goldeen 30% · Lv 5-10 +7 more
Trainers: Bug Catcher Rick Lv 4, Lass Tiana Lv 4, Youngster Allen Lv 5, Youngster Calvin Lv 5
Route 103
Wild: Magikarp 70% · Lv 5-10, Tentacool 60% · Lv 5-35, Wailmer 60% · Lv 25-45, Zigzagoon 60% · Lv 2-4 +4 more
Trainers: ★ Rival Brendan (Mudkip) Lv 5, ★ Rival Brendan (Torchic) Lv 5, ★ Rival Brendan (Treecko) Lv 5, ★ Rival May (Mudkip) Lv 5, ★ Rival May (Torchic) Lv 5, ★ Rival May (Treecko) Lv 5 +4 more
Route 104
Wild: Magikarp 100% · Lv 5-10, Wingull 95% · Lv 10-30, Zigzagoon 50% · Lv 4-5, Wurmple 30% · Lv 4-5 +2 more
Trainers: Fisherman Ivan Lv 6, Hiker Lucas Lv 9, Hiker Mike Lv 10, Lady Brianna Lv 10, Lady Cindy Lv 7, Lady Cindy Lv 11 +6 more
Pick up: TM09 Bullet Seed
Route 115
Wild: Wailmer 100% · Lv 20-45, Magikarp 70% · Lv 5-10, Tentacool 60% · Lv 5-35, Taillow 40% · Lv 23-25 +5 more
Trainers: Battle Girl Cyndy Lv 19, Black Belt Koichi Lv 26, Black Belt Nob Lv 20, Collector Hector Lv 20, Collector Hector Lv 20, Expert Timothy Lv 28
Route 116
Wild: Whismur 30% · Lv 6-7, Zigzagoon 28% · Lv 6-8, Nincada 20% · Lv 6-7, Taillow 20% · Lv 6-8 +1 more
Trainers: Bug Catcher Jose Lv 8, Hiker Clark Lv 8, Lass Janice Lv 10, School Kid Jerry Lv 10, School Kid Karen Lv 9, Youngster Joey Lv 10
Rustboro City
Wild: Anorith Lv 20, Lileep Lv 20, Makuhita Lv 5-100
Pick up: TM39 Rock Tomb, HM01 Cut

★ Rival Brendan (Mudkip) — Route 103

1 Pokémon · level cap Lv 5 (every cap) · Rival Brendan (Mudkip)’s own page

	Pokémon	Moves
	Mudkip Lv 5 · Torrent	Tackle Growl

★ Rival Brendan (Torchic) — Route 103

1 Pokémon · level cap Lv 5 (every cap) · Rival Brendan (Torchic)’s own page

	Pokémon	Moves
	Torchic Lv 5 · Blaze	Scratch Growl

★ Rival Brendan (Treecko) — Route 103

1 Pokémon · level cap Lv 5 (every cap) · Rival Brendan (Treecko)’s own page

	Pokémon	Moves
	Treecko Lv 5 · Overgrow	Pound Leer

Also fought around here

Rival May (Mudkip)Rival May (Torchic)Rival May (Treecko)

Everything you can have caught by this checkpoint · Open the interactive guide

This game's documentation doesn't say where 15 of its 396 fights happen, so those trainers are on no part of this walkthrough; they are all on the Trainers page. It also doesn't say when 4 of its areas open up, so they are listed together in the last part rather than guessed into the story.